Nobody likes morning sickness, but as they say, no pain, no gain. A quick and highly effective method to burn fat is to exercise intensely on an empty stomach. But make no mistake, having an empty stomach will prevent you from functioning optimally. The advantage you gain from such workouts is that you save time. Be sure to consult your doctor and get his/her approval before you do intense exercises.
There are quite a few books on high intensity interval training HIIT out there. Basically, it’s a cardiovascular exercise strategy alternating short periods of intense anaerobic exercise with less intense recovery periods, until too exhausted to continue. For amateurs, a session lasting 10-15min can yield amazing results.
It’s not a matter of having no time. It’s not a matter of having no endurance. HIIT requires discipline and grit. You just need to endure for those few minutes and you’re done.
There are many trainers out there who may not recommend a pre-breakfast workout. Personally, I think that HIIT should not be done on a full stomach. The rationale is this. When you wake up in the morning, your glycogen stores are almost depleted. The next thing your body draws on is fat. An intense workout will quickly deplete all your glycogen.

It gets really complicated when you read books. Here is a very simple method that works. Do a bit of warm up to make sure your ankles are not stiff. Start running, then sprint for 20 seconds. Slow down to a walk for 1-2 minutes. Sprint again as fast as you can for another 20 seconds, then walk, sprint, walk sprint. You’re quite good if you can last 10 minutes. If you have a gym membership with a nifty treadmill, you may even program the machine to give you different speeds and inclines at different intervals.
Another strenuous exercise you can do is to run up the stairs. I normally “hit a wall” when I reach the 10th floor. Walk down slowly, then run up again. I can’t do more than 4 reps at the moment. All this takes 15 mins or even less.
That’s it. You won’t feel very good after these workouts, maybe even nauseous (hence morning sickness), but it’s definitely worth the time. Rest awhile, drink some water and when you feel better, go for your breakfast.